>Hello everyone,
>
> Thanks in advance for any help.
>
> I have this ParametricPlot3D etc. plots from
>Mathematica 2.1 (RS/6000 version). I saved the
>output in PostScript, and the GhostScript-Ghostview
>combination is able to display the PostScript
>in color. In other words, the graphic is
>separated from Mathemtica. The problem is
>our hardcopy printer does not yet support
>color.
>
> How can I fool Mathematica to not use color
>in generating PostScript? Rather, grayscale
>PostScript is more desirable for printing
>on paper.
This is the purpose of ColorOutput which is an option of all
graphics functions.
The simplest way to use this for your purpose is
Show[ obj, ColorOutput -> GrayLevel]
this will use an internal conversion algorithm to ensure that only
PostScript commands setgray appear in the output.
If you want to supply your own function this can be done as so:
fun[ RGBColor[ r_, g_, b_]] := GrayLevel[ (r+g+b)/3.]
fun[ g_GrayLevel] := g
Show[ obj, ColorOutput -> fun]